A rotary compressor is mainly applied to an air conditioner. Recently, as the air conditioner has various functions, a capacity variable type rotary compressor is being required.
As technique for varying a capacity of the rotary compressor, an inverter method for controlling rpm of the rotary compressor by applying an inverter motor has been well known. However, the technique has the following disadvantages. First, since the inverter motor is expensive, a fabrication cost is increased. Second, since the air conditioner is used as a cooling apparatus, a process for enhancing a cooling capability in a cooling condition is more difficult than a process for enhancing a cooling capability in a heating condition.
Accordingly, recently, a cooling capability varying technique by an exclusion capacity switching (hereinafter, will be called as an exclusion capacity switching technique) for varying a capacity of a compression chamber by bypassing a part of refrigerant gas compressed in a cylinder outside the cylinder is being introduced instead of the inverter method.
As the exclusion capacity switching technique, a digital compression technique for controlling a cooling capability by combining a saving driving (hereinafter, ‘mode 0 driving’) for making a cooling capability be zero by temporarily stopping a compressor being operated with a power driving (hereinafter, ‘mode 1 driving’) for driving a compressor with 100% is being introduced.
For example, if the mode 1 driving is performed for 7 seconds and the mode 0 driving is performed for 3 seconds, a cooling capability corresponding to 70% is obtained for the total 10 seconds. A compressor for controlling a cooling capability by controlling the mode 1 driving and the mode 0 driving by time is called as a digital compressor. The digital compressor can be fabricated with a cheap cost since an inverter is not required, and has an excellent efficiency and reliability.
However, most of the digital compression techniques have not been applied to a concrete driving mechanism of a rotary compressor whereas the digital compression technique has been applied to a scroll compressor for utility.